Characterization of polyolefins-based pyrolysis oils: A comparison between one-dimensional gas chromatography and two-dimensional gas chromatography

The characterization of pyrolysis products is essential for the development of precise and accurate kinetic models. The resolution of pyrolysis products analyzed using traditional analytical methods may be compromised, resulting in inaccurate product identification and overlapped peaks. This study investigated the product distribution of pyrolysis oil derived from plastics using two analytical techniques: one-dimensional gas chromatography coupled with mass spectrometry (GC–MS) and two-dimensional gas chromatography coupled with flame ionization detector and time-of-flight mass spectrometer (GC×GC–FID/TOF–MS). Pyrolysis experiments of polypropylene (PP), high-density polyethylene (HDPE), polystyrene (PS), as well as co-pyrolysis of PP–PS and HDPE–PS, were conducted at 500 °C using a micropyrolyzer coupled with GC and GC×GC. GC×GC enabled the peak identification 2.8, 5.3, 4.8, 3, and 4.1 times more compared to GC in the pyrolysis of PP, HDPE, PS, PP–PS, and HDPE–PS, respectively. The yield of new chemical classes was found to be 1.3, 5.6, 0.2, 0.8, and 1.5 wt.% for pyrolysis of PP, HDPE, PS, PP–PS, and HDPE–PS, respectively. Furthermore, new products were detected in the co-pyrolysis of PP–PS (1:1), with a total yield of 0.5 ± 0.07 wt.%. Additionally, interaction effects were observed in the co-pyrolysis experiments, such as a 29.7% and 51.3 % increase in the experimental yield of toluene compared to the additive yield for PP–PS and HDPE–PS co-pyrolysis, respectively, which can be attributed to secondary reactions involving the consumption of styrene.